Passing Core Web Vitals: a practical field guide

Core Web Vitals reward sites that feel fast and stable. They're a modest ranking factor, but a large conversion factor: every hundred milliseconds of delay costs you trials, signups, and sales. Here's how to pass all three without chasing a perfect lab score you'll never keep.

LCP: make the main content appear fast

Largest Contentful Paint measures when the biggest visible element loads. The usual culprits are heavy hero images, slow servers, and render-blocking resources. Fixes that reliably help:

• Serve hero images as compressed WebP or AVIF, correctly sized, and mark them high-priority.
• Put a CDN and sensible caching in front of your pages.
• Remove render-blocking CSS and defer non-critical scripts.

INP: keep the page responsive to input

Interaction to Next Paint replaced First Input Delay and is stricter. It measures how quickly the page responds when someone taps or clicks. The fix is almost always the same: ship less JavaScript, break up long tasks, and avoid heavy work on the main thread during interactions.

CLS: stop the layout from jumping

Cumulative Layout Shift punishes content that moves as the page loads. Reserve space for images and embeds with explicit dimensions, avoid inserting content above existing content, and preload web fonts to prevent text reflow.

Measure field data, not just the lab

Lighthouse gives you a lab snapshot; the Chrome User Experience Report and Search Console give you real-user field data, which is what Google actually uses. Optimise for field data and re-check after every release, because performance regresses quietly.

Speed is a design decision

The fastest sites are fast by design, not by last-minute optimisation. Performance budgets, a restrained component library, and disciplined third-party scripts do more than any plugin. This is central to our web design and development work, and it pairs tightly with technical SEO.

Want your site audited against all three vitals? Tell us about your site and we'll prioritise the fixes with the biggest impact.